RNG in MM4 is dictated by 4 bytes @ $E4-E7 that are changed with each frame. In addition, there are certain points (i.e., boss fights) in the game that internally modify the bytes
to prevent timing attacks. Manipulation is not feasible outside of a TAS, so we must modify specific code segments to alter the use of RNG.

1. Dust man: Suck event has a 1/4 chance.						
0xAD28
  LDY #$03                 
  BNE $AD34                
  DEC $0468,X              
  BNE $AD4C                
  JSR $B71E                		; RNG
  LDA $AE42,Y              		; 14 15 14 13  	15 14 14 14		13 15 13 14 	14 13 13 15 	14 13 15 14 	13 14 15 13
  JSR $F446                		; 15 = suck, 6/24; 13 = dust shot, 14 = jump
  LDA $0558,X              
  AND #$03                 
  TAY                      
  LDA $AE5A,Y              
  STA $0588,X              
  LDA $AE5E,Y              
  STA $05A0,X              
  RTS       

********************************************************************************************************************************

2. Skull man: Skull shield can vary from 0.5 - 4.25s.						
0xA8B2
  LDA $E4                  
  ADC $E6                  
  STA $E6                  		; update RNG byte 3
  AND #$07                 
  TAY                      		; Delay table for skull shield:
  LDA $AA5C,Y              		; 40 FF A0 20 FF 70 30 5A
  STA $0468,X              		
  LDA #$E4                 
  STA $0588,X              
  LDA #$A8                 
  STA $05A0,X              
  RTS          

********************************************************************************************************************************  

3. Drill man: Primary action table is 3 options, 2A/2F/30. Dive(2A) starts a timer of 210f (3.5s) once he disappears underground. Your x-coord is queried at 30f (0.5s) before he reappears.
0xB045
  LDA #$B8                 
  STA $EF                  
  LDY #$01				; hardcoded initial dive            
  BNE $B055                		; skip RNG
  DEC $0468,X              		
  BNE $B06D                		
  JSR $B71E                		; RNG
  LDA $B28F,Y              		; 2F 2A 2F 30 	2A 2F 30 2F 	30 2A 30 2F 	30 2A 2A 30 	2F 2A 2A 30 	2F 2F 2A 2A
  JSR $F446                		; 2A = dive (9/24 chance), 2F = jump, 30 = bombs
  LDA $0558,X              		
  AND #$03                 		
  TAY                      
  LDA $B2A7,Y              		
  STA $0588,X              		
  LDA $B2AB,Y              		
  STA $05A0,X              		
  RTS                      

********************************************************************************************************************************

4. Square machine: Odds of a 1-1 pass are 1/64.
0xBB94
  LDA $E4                  
  ADC $E6                  
  STA $E6                  		; update RNG byte 3
  AND #$07                 
  TAY                      		; Pass table:
  LDA $BD4F,Y              		; 00 01 01 01 02 02 02 02
  STA $0468,X              		; 1 = 1/8, 2 = 3/8, 3 = 4/8
  LDY $0468,X              
  LDA $BD49,Y              		
  STA $03A8,X              
  LDA $BD4C,Y              		
  STA $03C0,X              
  RTS                      

********************************************************************************************************************************

5. Met Man: Open/close duration

0xA127
  LDA $E4                  
  ADC $E5                  		; update RNG byte 2
  STA $E4                  
  AND #$01                 
  TAY                      		; Open duration
  LDA $A354,Y              		; Look-up table: 3C 78
  STA $0468,X              		; Either 1 or 2s

0xA26F
  LDA $E4                  
  ADC $E5                  		; update RNG byte 2
  STA $E4                  
  AND #$01                 
  TAY                      		; Close duration
  LDA $A352,Y              		; Look-up table: B4 F0
  STA $0468,X              		; Either 3 or 4s

********************************************************************************************************************************

6. Tako Trash: Fireball/bomb

0xA52B
  LDA $E4                  
  ADC $E6                  		; update RNG byte 3
  STA $E6                  		; 50/50 chance
  AND #$01                 		; change #$01 to 00 for fireball, FF for bomb
  BNE $A559                		

********************************************************************************************************************************

7. Dr. Wily: Spawn location, hitbox duration, respawn delay

Spawn location

0xB529
  LDA $E4                  
  ADC $E5                  		; update RNG byte 2
  STA $E4                  
  AND #$0F                 	
  TAY                      
  LDA $B8AA,Y              		; Spawn location table: 01 00 01 07 02 06 03 05 04 03 05 02 06 01 07
  ASL A                    
  TAY                      
  LDA $B890,Y              		; Load YX coords based on above value:
  STA $0378,X              		; YX pairs: 48 54 40 84 30 D4 70 44 88 7C 70 BC D0 34 C0 B4
  LDA $B891,Y              
  STA $0330,X              

Hitbox duration / Respawn delay

0xB5D8
  LDA $E4                  
  AND #$01                 
  TAY                      
  LDA $B912,Y             		; Hitbox duration table: 3C 5A 
  STA $0468,X              		; 1 or 1.5s
  LDA $E5                  
  AND #$01                 
  TAY                      
  LDA $B914,Y              		; Respawn delay table: 3C 96
  STA $0480,X              		; 1 or 2.5s

********************************************************************************************************************************

v1: Initial release.
v2: Added support for Met Man, Tako Trash, Dr. Wily. Added javascript randomizer for customization:
	https://jeboo.github.io/mm4_derng/